High-frequency wave-signal tuning device



Oct. 27, 1959 M. PRESS 2,910,658

HIGH-FREQUENCY WAVE-SIGNAL TUNING DEVICE `Original Filed Jan. 1l, 1955 2 Sheets-Sheet 1 cINTERMEDLFE u DETECTOR V DE()- FREQUENCY AND A.G.C. FREQUENCY n AMgLlFlER D SUPDPLY AMPLiFlER Frequency (Megacycles) lOut l'n Posilion of Tuning Means 36 34 {35 o swrNcHrcNlzll os Nml -slGN L. Y Z osclLLAToR AMPUFER D 5|GNAL sEPARAToR SEPARTOR GENERATOR F|G.1 *i* Oct. 27,` 1959 M. PRESS HIGH-FREQUENCY WAVE-SIGNAL TUNING DEVICE 2 Sheets-Sheet 2 Original Filed Jan. l1, 1955 United States Patent C HIGH-FREQUENCY WAVE-SIGNAL TUNING DEVICE Meyer Press, Sharon, Mass., assignor to'Hazeltine Research, Inc., Chicago, Ill., a corporation of Illinois` Continuation of applicationSei-ial No. 484,279, January 11, 1955. This application October 9, 1958, Serial ',No. 766,271

General.

rected'to tuning devices which are capable of having .de`

sired tuning characteristics. Such a tuning.device may` have particular utility ina television receiver and, accordingly, will be describedin that environment.

This application` is acontinuationinwhole of. application Serial No. 484,279, tiled January.` ll, 1955, now abandoned, and entitled High-Frequency Wave-Signal Tuning Device. A

In high-frequency wave-signal receivers'hayingntuning devicesV which utilize transmission lines'as tuned.`circuits,. various systems have been devised to provide n desired` tuning characteristics for the adjustably tunedclrcuits of the receivers. Some prior systems have utilized rotatablev discs or plates having preselected shapes which maybe inserted in controllable amounts between the conductors of the transmission lines to provide desiredtuning characteristics therefor. Other systems have utilized in'eachA thereof a tuningslug displaceable longitudinally of the transmission line and over a portion thereof having im pedance continuity along the length of` thatportion.` While these prior systems in thetuning devices have been. effective to tune the transmission lines thereof, they have been somewhat unsatisfactory for Lsome applicationsin that theV tuning characteristicsforthe devices and par-` ticularly'` the slopes thereof may be modifiedv only to a limited extent over the high-frequency portions.of `the tuning ranges.

It is an object ofthe present invention, therefore, to provide a new and improvedhigh-frequency wave-signal tuning device which avoids the above-mentioned disadvantage ofprior such systems.`

It is another object of the invention to provide for use in a television-receiver a new and improved high-frequency wave-signal tuning device which is simple in` construction yet is capable of providingl for the receiver.

a `desired tuning characteristic.

It is a further object ofthe invention to provide for use in a television receiver an inexpensive high-frequency wave-signal tuning device which is capable of providing a high degree of control of the tuning characteristic of the receiver over the high-frequency portion of itsI tuning range.

In accordance having an elective` electrical length approximately equal to an integral multiple of one-quarter wavelength at` a predetermined frequency inthe aforesaid range. The.

transmission line includes a'pair of elongatedconductors,

ice

atleast oneof said conductors havingan attenuated end portion.` The tuning device includes reactive tuning means displaceable at least along the above-mentioned portion of the conductors for primarily varying the capacitance between the tuning-means and the conductors with displacement of the tuning means selectively to ad# just the effective electricallength of the transmissionline to substantially the aforesaid multiple of one-quarter wavelength at: each frequency in-the above-mentioned range to tune the transmission line in a desiredmanner:

Foi-.a better understanding ofthe present invention, togetheriwithother and further objects thereof, reference is. had.to the following description takenin connectionk withthe.accompanying-` drawings, and'its scope will'be pointed out in ithe appendedlclaims.

In'the accompanying drawings, Fig. 1 is a circuit'di'agram, partly schematic, of acomplete television receiver includingia tuning device in accordance with a particular form ofith'einvention. Fig. 2"is a graph utilized inV explaining thel operation of 1 the tuning device ofthe Fig: 1 receiver. Figs. 3-5, inclusive, are fragmentary perspectiveviewsof' tuning devices illustrating modieationslof the invention;

Referringnow more particularly to Fig. l ofthe draw ings, thev complete` television` receiver there represented comprises an 1 antenna: system 10, 11A and la coupling loop 12:coupled:.to a high-frequency Vwave-signal tuning device 13%eornprising a resonant transmission line which irrcludesconductors 14k-'and 15; Then tuning device- 13i includes a movable :tuningmeans 16 connectedlto la rack-l' 17ofinsulating material; Rack 17 engages with aipinion` gear. 18nto provide.longitudinallmovernent of the tuning means 16y along thetransmission line comprisingthe conductorszy 14"? and? 15. Ai suitable bracketV 191 supports the tuning means 16, the rack 17 andthe `.gear 1S".` They tuning device 13, which embodies thepresentdnvention, will subsequently b'e described in greater detail.

Az frequency-converter` systemV including a. condenser` 24`fand-acrystal ,mixer 25 is coupled to the tuning device 13 in a conventionalmanner.andpreferably at a position on the'transmissionzline.14, 15 selected toprocure an; impedance matchi between the transmissionline 14,` 15 andthe frequencyfconverter system 24; 25'. The condenser 24` is coupledthrough a pair of output terminals Z6, 26. in cascadeand` in the order named to an inter# mediate-frequency amplifier 27 'of one or more stages,` a' detector and automatic-gain-controllor A.G.C. supply 28,` a video-frequency amplifier. 29l of one or more stages;

and an imagefreproducing device 30iwhich-` maycom-` prise a cathode-ray tube.` The A.G.C. supply circuitof unit=281is ,connected to the input circuit of one or more'V stages` of` the intermediateefrequency amplifier 27`Vby a control circuit conductor 31.

The output circuit. ofi the video-frequency ampliiier 29 is coupledto the input circuit ofa line-frequency gen=` erator 32 and a held-.frequency generator 33 through a-v synchronizing-signal amplifier and separator 34 andan intersynchronizing-signal'separator 3S. The output cir-l cuits ofthe generators 32'and 313 are coupled in a convenL tional manner to scanning coils of the device'30. The television receiver also includesan oscillator 36 coupled. through a pair of input'terminals 37,` 37 'to the mixer 25; All of the described units, exclusive of the tuning device 13, `may be of conventional construction and operation so thata detailed.` description of the operation thereof.

is unnecessary. v

Consideringbriefly, however, the general'operation of' thegabove-describedreceiver as a whole, wave signals in-L tercepted by the-antennasystem 10; 11 are translated by thefcoupling loop 12'and.tothe tuning device 13. The tuning` device-13 p isadjusted to `resonate atv the 'frequencyi of a selected wave signal by rotating the pinion gear 18 which in turn actuatesthe rack l17 yand adjusts the position of the tuning means 16 with reference to the transmission line 14, 15. The local oscillator 36 is adjusted by suitable means (not shown) simultaneously with the adjustment of the 'tuning means 16 and provides for Vthe mixer 25 at input terminals 37, 37 a heterodyne wave signal which beats with the received wave signal in the frequency-converter system 24, 25. Through ythe wellknown heterodyne action in the frequency converter system 24, 25, an intermediatefrequency signal is applied to the input circuit of the intermediate-frequency amplifier 27. This signal in turn is selectively amplified in the intermediate-frequency amplifier 27 and delivered to the detector and automatic-gain-control supply 28. The modulation components of the signal are derived by the detector 28 and are supplied to video-frequency amplifier 29 wherein they are amplified and from which they are applied to the input circuit of the image-reproducing device 30. A control ,voltage derived by the automaticgain-control supply of unit 2S is applied as an automaticamplification-control bias to the gain-control circuits of the intermediate-frequency amplifier 27 to maintain the signal input to the detector of unit 28 within a relatively narrow range for a Wide range of received signal intensities.

Unit 34 selects the synchronizing signals from the other modulation components of the composite video-frequency signal applied thereto by the video-frequency amplifier 29. The line-synchronizing and field-synchronizing signals derived by the separator 34 are separated from each other by unit 35 and are then supplied to independent ones of the generators 32 and 33 to synchronize the operation thereof. Saw-tooth current Waves are generated in the generators 32 and 33 and are applied to the scanning coils of the image-reproducing device 30 thereby to deect the cathode-ray beam of that device in two directions normal to each other to trace a rectilinear scanning pattern on the screen of the device and thereby reconstruct the translated picture.

Description of tuning device of Fig. I receiver Referring now more particularly to the tuning device 13 which embodies the present invention the device 13, which is tunable to each of a plurality of wavelengths in a selected range of wavelengths, comprises the pair of elongated conductors 14 and 15 which are ordinarily parallel' conductors having a rectangular cross-section. The conductors 14 and 15 preferably have a low-impedance termination at one end thereof provided by a conductor 38. The transmission line includes a portion 39 preferably at the other end of the conductors 14 and 15 forming a high impedance termination and presenting an impedance discontinuity. The transmission line 14, has an effective electrical length approximately equal to an integral multiple, which is preferably an odd multiple, of one-quarter of a predetermined wavelength in the selected range of wavelengths. As used in this specication and the claims, the term integral multiple is employed in its usual sense and is also meant to include the product obtained by utilizing unity as a multiplication factor. The effective electrical length of the transmission line 14, 15 preferably is approximately equal to onequarter of the shortest wavelength in the selected range.

At least one of the tuning means 16 and the pair of conductors 14 and 15 include an attenuated end portion. In the embodiment illustrated in Fig. 1, the tuning means 16 is provided with an attenuated end portion 41. The end portion 41 preferably is tapered and ymay have a substantially pyramid shape. This end portion is disposed longitudinally of the conductors 14 and I15 preferably with the taper thereof extending towards the end of the conductors 14 and 15 having the low-impedance termination 38. The tuning means 16'for the tuning device 13 may be made of conductive or dielectric material and has a pair of slots 40, 4f) therein (only one kof which may be seen) for engagement with the conductors 14 and 1'5. When the tuning means is made of conductive material, suitable insulating strips 42V are employed in the slots physically to separate the member k16 from the conductors 14 and 15.

The tuning means 16 is displaceable at least along the portion 39 of the transmissionv line 14, 115 and preferably beyond the'portion 39 to a position of complete disengagement with the'transmission line. The tuning means 16 presents a reactive impedance across the transmission line for selectively adjusting the effective electrical length thereof to the aforesaid multiple of lone-quarter wavelength at each of the plurality of wavelengths in the selected range. Accordingly, the tuning means 16 at each position of adjustment thereof selectively adjusts the effective electrical llength of the transmission line 14, 15 Ito one-quarter wavelength at each of the plurality of wavelengths in the selected range.

Operation of Fig. l timing device The operationof the tuning device represented in Fig. 1 and the results obtainedthereby may be best understood by reference to Fig. 2 of the drawings. Curve A of Fig. 2, shown in solid-line construction, represents the tuning characteristic of the tuning device 13 utilizing the tuning means 16. Curve B of Fig. 2, shown in broken-line construction, represents the tuning characteristic of the tuning device 13 utilizing a tuning means which is also constructed in accordance with the invention but having an end portion with less taper than the portion 41 represented in Fig.v 1.

As the tuning means 16 of Fig. 1 is moved from the position shown in that figure, which position corresponds to the one designated Out in Fig. 2, to a position of complete engagement with the transmission line 14, 15, which position then corresponds to the one designated In in Fig. 2, the resonant frequency of the transmission line decreases from a frequency fd to a frequency fc, as represented by curve A of Fig. 2. The tuning means 16 may be considered as effectively introducing capacitance in the region of high electric-field intensity at the portion 39 of the conductors 14 and 15. As the tuning means 16 is displaced along the portion 39 toward conductor 38, the capacitance introduced thereby increases in a manner determined by the shape of the end portion 41 and causes an effective lengthening of the transmission line 14, 15. The resonant frequency of the transmission line is decreased by the displacement of the tuning means 16 as represented by curve A.

Considering now the effect of utilizing a tuning means in accordance with the invention but having less taper than the tuning means 16, the tuning characteristic for the device 13 is then represented by curve B as previously mentioned. It is evident that as such a tuning means is displaced at the portion 39 and toward conductor 38,` the capacitance effectively introduced thereby increases more rapidly than the capacitance introduced by the tuning means 16 as described above. The effective electrical length of the transmission line 14, 15 now increases and the resonant frequency` thereof now decreases more rapidly than previously, as may be seen from curve B of Fig. 2. Accordingly, over the high-frequency portion of the tuning range, the slope of the tuning characteristic represented by curve B is substantially greater than the slope of the tuning characteristic represented by curve A. Preselection ofthe shape of the tuning means 16 thereby provides over the high-frequency portion of the tuning range a high degree of control of the tuning characteristic of the tuning device 13. Accordingly, the tuning means 16 causes the effective electrical lengths of the transmission line 14, 15 at each position of the tuning means to alter in a desired manner.

The .tuning devices of Figs. 3, 4 and 5 represent modifications of the present invention and are generally similar to that vof Fig. 1, corresponding elements being designated by the same reference `numerals and similar i elements -by similar-reference numeralsincreased. in value by the factor 300, 400, or 5.00, as the case maybe. Eachiof these devices will `be described inturn hereinafter.

Description o'f Fig. 3 tuning device Referring now to Fig. 3 of the drawings,v the tuning device v313 there represented comprises a transmission line having an effective electrical length approximately equal to an integral odd `multiple of one-quarter of a predeterminedwavelength in a selected range of wavelengths. The tuning device includes a pair of elongated conductors 314 and 315 having a low-impedance termination provided by conductorSS at one end thereof. The transmissioniline 314, 31'5'h'as a portion 339. at the other end thereof having ahigh-impedance'termination presenting an `impedance discontinuity. The pair of conductors 314and315 has an attenuated end portion 320 adjacent the` high-impedance termination. The attenuated end portion'3`20 of atleast one of the pair of conductors 314 and 315 is taperedV with the taper thereof extending toward the above-mentioned other end of the conductors having the high-impedance termination. A uniformly shaped tuning means 316, preferably of dielectric or conductive material, has a pair of bores 340 provided with insulating sleeves 342 therein for receiving the conductors 314 and 315. The tuning means 316 is displaceable at least along` the attenuated end portion 320 for selectively adjusting the effective electrical length of the transmission line 314, 315 to the last-mentioned multiple of onequarter wavelength at each of the wavelengths in the lastmentioned selected range of wavelengths. The operation of the tuning device 313 is generally similar to the operationV of the tuning device 13 of the Fig. l embodiment and a detailed explanation thereof is deemed unnecessary. Briefly, however, adjustment of the tuning means 316 causes the effective electrical lengths of the transmission line 314, 315 at each position of adjustment of the tuning means 316 at the attenuated end portion 320 to alter in a desired manner.

Description of Fig. 4 tuning device The modification of the Fig. 4 embodiment is identical with that of the Fig. 3 embodiment except for the shape and position of tuning means 416. Each of the pair of conductors 414 and 415 and the tuning means 416 includes a tapered end portion, each conductor having a tapered end portion 420 and the tuning means having a tapered end portion 441. The tapered end portions 441 vand 420 are disposed longitudinally of the conductors 414 and 415 with the tapers of the tuning means 416 and the pair of conductors 414 and 415 extending in opposite directions. The tuning means 416 may be disposed below the transmission line 414, 415 to provide capacitive tuning therefor. The operation of tuning device 413 is generally similar to the operation of the tuning devices of Figs. l and 3 so that further explanation thereof is deemed unnecessary.

Descrption of Fig. 5 tuning device The tuning device of Fig. 5 diifcrs from those of the previously described figures in that the tuning device 513 utilizes a tuning means 516 of magnetic material. The tuning device 513 comprises a transmission line including a pair of elongated conductors 514 and 515. The transmission line 514, 515 also has an effective electrical length approximately equal to an integral even multiple of one-quarter of a predetermined wavelength in a selected range of wavelengths. The predetermined Wavelength may be preferably the shortest wavelength in the selected range. The conductors 514 and 515 have a low-impedance termination 521 presenting an impedance discontinuity and have an attenuated end portion 520 adjacent the low-impedance termination 521. The tuning means p 516 may be disposed below the transmission line 514, 515

and is-displaceable at leastalongl `the attenuated end portion 520 for selectively adjusting theetective electrical lengthV of the transmission `linew514, 515to the lastmentioned multiple of one-quarter `-wavelength at yea'chof the wavelengths `in `the last-mentioned selected range of wavelengths. j

The operation of the'Fi-g. V5 tuning device is generally similar to the operation of the Fig. l embodiment.` Displacement-of the tuning means 516 from a region of low magnetic-field intensity into ahregion of high magneticfield- -intensityalong ythe attenuated-endv portion 520 of the conductors S14-,i515 causes ia gradual change in the magnetic-field vdistribution `and lengthens` the effective electrical length of the transmission line 514, 515. Inductive tuningisthereby effectively provided'for the tuning device 513. Accordingly, `the tuning Ymeans 516 causes the` .effective electrical `lengths' of the transmission line 514,- 515 at eachfpositionfof adjustment of the tuning means to alter in adesired manner.

From rthe foregoing description `of the invention, it will Abe apparent that a tuning device embodying the invention has the advantage that it provides for a television receiver a tuning characteristic represented by a curve having a desired slope over the high-frequency portion of the tuning range.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled inthe art that various changes and modifications .may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes; and modifications as fall within the true spirit and scope of the invention.`

What is claimed is:

l. A high-frequency wave-signal tuning device tunable over a selected frequency range comprising:` a transmission line having an effective electrical length approximately equal to an integral odd multiple of one-quarter wavelength at a predetermined frequency in said range and including a pair of elongated conductors having a low-impedance termination at one end thereof and having at the other end thereof a high-impedance termination presenting an impedance discontinuity and having a tapered end portion adjacent said high-impedance termination with the taper thereof extending away from the low-impedance termination; and tuning means displaceable at least along said tapered end portion of said conductors for selectively adjusting the effective electrical length of said transmission line to substantially said multiple of one-quarter wavelength at each frequency in said range, said tuning meansI and said conductors comprising an effective condenser having a value which increases with displacements toward said one end of said conductors and providing a frequency-displacement tuning characteristic which decreases in frequency with said displacements toward said one end of said conductors to tune said transmission line in a desired manner.

2. A high-frequency wave-signal tuning device tunable over a selected frequency range comprising: a transmission line having an effective electrical length approximately equal to an integral multiple of one-quarter wavelength at a predetermined frequency in said range and including a pair of elongated conductors, at least one of said conductors having an attenuated end portion; and reactive tuning means idisplaceable at least along said portion ofsaid conductors for primarily varying the capacitance between said tuning means and said conductors with displacements of said. tuning means selectively to adjust the effective electrical length of said transmission line to substantially said multiple of onequarter wavelength at each frequency in said range to tune said transmission line in a desired manner.

3. A high-frequency wave-signal tuning device tunable to each of a plurality of wavelengths in a selected range of wavelengths` comprising: a transmission line having `an eiective electrical length approximatelyequal ytdan integral multiple of one-quarter of a predetermined Wvelengthin said range and including a pair'of elongated' -coiiduct'orsgand reactive tuning means of magi netiomaterial displaceable along jsaid transmission line ror selectively adjusting the effective electrical length of said` transmission line to substantially said multiple of one-quarter wavelength at said each `of said plurality of wavelengths in said range; at least one of said pair of conductors including an attenuated portion disposed lon- 'gitudinally of said conductors for causing said effective electrical lengths of said transmission line at each position of adjustment ltof said tuning means to alter in a desired manner. v f

4. A high-frequency wave-signal tuning device tunable to each o f a Vplurality of wavelengths in a selected range of wavelengthscomprising: a transmission line having an effective electrical length approximately equal to an 'integral even multiple of one-quarter of a predetermined wavelength in said range and including a pair of elongated conductors having a low-impedance terjustment of said tuning means to alter in a desired man? ner. Y References Cited in the file of this patent V UNITED STATES PATENTS 2,160,466 Usselman May 30,' 1939 2,370,423 Roberts Feb. '27, "1945 2,627,579 Wasmansdortf Feb. 3, 1953 2,682,642 Podolsky June 29,'1954 Murakami Aug. 9,' 1955 l die. 

